The prior art electrical means of generating mechanical braking torque have generally involved application of alternators, generators, motors, eddy current drives, and magnetic brakes. These traditional designs are all limited due to the relatively high cost of the required components, circuit complexity, large physical size, power dissipation, and restricted speed and torque ranges. Often high electrical currents and large voltage pulses have resulted in poor reliability and also emitted large quantities of electromagnetic interference (EMI). Audible noise as well as mechanical vibration and the associated power losses have further reduced the effectiveness of these conventional torque generating devices due to rotational components in the drive lines and the requirement for large gear ratios. With this background, it is apparent that a new method of braking torque generation is required.
In one conventional electronic device for providing mechanical braking torque, an alternator is used with two electronic regulators typically being required, one to maintain a constant output voltage from the alternator and a second to regulate the load current flowing through a load resistor. Voltage and current are separately regulated. The total power dissipation is the product of the output voltage times the load current. There are a number of disadvantages to such prior art devices, including, for example, instability and reliability, circuit complexity, high alternator output currents under heavy loads, high power dissipation in general and usually confinement of power dissipation to parts that have small surface areas and, therefore, excessively heat, poor low rpm performance, small dynamic load range, and large initial mechanical load.